The problems presented by substances which deplete the atmospheric ozone layer were dealt with at Montreal, where the protocol was signed imposing a reduction on the production and use of chlorofluorocarbons (CFCs). This protocol has formed the subject of amendments which have required the abandoning of CFCs and have extended regulation to other products, including hydrochlorofluorocarbons (HCFCs).
The refrigeration and air conditioning industries have invested a great deal in the replacement of these refrigerants and it is because of this that hydrofluorocarbons (HFCs) have been marketed.
In the motor vehicle industry, the air conditioning systems of commercial vehicles have been changed in many countries from a refrigerant comprising chlorofluorocarbon (CFC-12) to that of hydrofluorocarbon (1,1,1,2-tetrafluoroethane: HFC-134a), which is less harmful to the ozone layer. However, from the viewpoint of the objectives set by the Kyoto protocol, HFC-134a (GWP=1430) is regarded as having a high heating power. The contribution to the greenhouse effect of a refrigerant is quantified by a criterion, the GWP (Global Warming Potential), which summarizes the heating power by taking a reference value of 1 for carbon dioxide.
Hydrofluoroolefins (HFOs) have a low heating power and thus meet the objectives set by the Kyoto protocol. The document JP 4-110388 discloses 2,3,3,3-tetrafluoropropene (HFO-1234yf) as heat transfer agent in refrigeration, air conditioning and heat pumps.
In addition to having good properties as a heat transfer agent, in order for a refrigerant to be accepted commercially, it must in particular be thermally stable and be compatible with lubricants. This is because it is highly desirable for the refrigerant to be compatible with a lubricant used in the compressor present in the majority of refrigeration systems. This refrigerant and lubricant combination is important for the use and the effectiveness of the refrigeration system; in particular, the lubricant has to be sufficiently soluble in the refrigerant throughout the operating temperature range.
According to the document WO 2008/042066, as fluoroolefins are capable of decomposing on contact with moisture, oxygen or other compounds when they are used as refrigerant, possibly at high temperature, it is recommended to stabilize them with at least one amine.
Other stabilizing agents, such as benzophenone derivatives, lactones and some phosphorus-comprising compounds, have also been proposed for stabilizing fluoroolefins (WO 2008/027596, WO 2008/027516 and WO 2008/027515).
Furthermore, the document EP 2 149 543 describes a process for the purification of 1,1,1,2,3-pentafluoropropane, a starting material in the manufacture of HFO-1234yf, in order to obtain a product having a 1,1,1,2,3-pentafluoropropene (HFO-1225ye) content of less than 500 ppm and a trifluoropropyne content of less than 50 ppm.